A facile method to prepare hydrophobic nanoparticle dispersions for controlled release

Using ethyl acrylate and methyl methacrylate as hydrophobic monomers, a series of hydrophobic nanoparticle dispersions were prepared by one-step polymerization (i.e., soap-free batch emulsion polymerization). To obtain stable aqueous nanoparticle dispersions, a small amount of ionic comonomer, sodium 4-ω-acryloyloxyβ-hydroalkyl sulfonate (Cops-1) was used. The nanoparticles were characterized by TEM, Zetasizer and DSC. It was found that number average diameter (D̄_n) values range from 144 to 202 nm at 25°C, and the diameter distribution [D̄_v/D̄ _n) from 1.11 to 1.14. These results indicate that the nanoparticles show a narrow distribution of sizes. Zeta potentials of the obtained nanoparticles are in range of -38.8 to -29.7 mV at 25°C. This suggests that they can be well dispersed in water. Using salicylic acid (SA) as model drug molecules, a novel swelling method was developed for loading SA into the nanoparticles in an aqueous dispersion state, and both related loading processes and controlled release behavior were investigated. It was found that the nanoparticles can sustain SA release, and compared to different types of nanoparticles, PMMA nanoparticles can retard SA release more effectively.